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Electrical and thermal percolation in carbon nanotube- polymer composites


Electrical and thermal properties of carbon-nanotube (CNT) /polymer composites were investigated through percolating behavior of conducting fillers in insulating matrix. Synthesis methodology has been found using a blend of solution processing, which was adapted to facilitate uniformly distributed CNTs in polymer matrix and consequently to contribute to percolation. The onset of percolation thresholds depending on aspect ratio of fillers were theoretically estimated by the excluded volume method as well as experimentally examined with a power relation of the both electrical and thermal conductivities. Consistent modeling of the both electrical and thermal conductivity anisotropy, in addition to the incorporation of interfacial resistance between connected conducting CNT fillers, was used to understand the underlying transport mechanisms and variations. Furthermore, we report a decrease in the specific heat capacity of the composites at a particular nanotube filler fraction, corresponding to the electrical and thermal conductivity percolation threshold. Extensive calibration and characterization of two different methods were accomplished for the specific heat capacity measurement, and degree of crystallinity through x-ray diffraction implied how degree of disorder would alter depending on arranging nanotubes in the polymer matrix. We explained such change in terms of the entropic configuration determined by number of isolated or connected nanotube fillers. Our investigations could yield better insight into percolation phenomena, of wide importance in the theory of networks, and the optimal conditions of CNT connectivity and dispersion for various applications

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